Apparatus for projecting cylindrical objects as circular images



Y aura Oct. 17, 1967 Filed June 50, 1966 LIGHT l SOURCE M. L. NOBLE APPARATUS FOR PROJECTING CYLINDRICAL OBJECTS AS CIRCULAR IMAGES 2 Sheets-Sheet 1 INVENTOR'. MILTON L. NOBLE,

HIS ATTORNEY.

Oct. 17, 1967 M. NOBLE 3,347,133

APPARATUS FOR PROJEGTING CYLINDRICAL 1 OBJECTS AS CIRCULAR IMAGES Filed June 30, 1966 2 Sheets-Sheet 2 BYW ' HIS ATTORNEY.

United States Patent 3,347,133 APPARATUS FOR PROJECTING CYLINDRICAL OBJECTS AS CIRCULAR IMAGES Milton L. Noble, 5 Ilex Lane, Liverpool, NY. 13088 Filed June 30, 1966, Ser. No. 561,912 15 Claims. (Cl. 88-24) The present application for US. Letters Patent is a continuation-in-part of applicants copending application for US. Letters Patent, Ser. No. 503,343, filed October 23, 1965, now abandoned, and assigned to the assignee of the present invention.

The invention relates to large screen, bright display projection systems of the type employing a light modulating medium for modulating a source of projected light so as to provide a large area, high intensity display of information applied to said medium. In particular, the invention relates to a novel PPI projection system of this type.

Considerable effort has been expended by workers in the field toward the accomplishment of a large screen PPI projection. However, none of the approaches thus far taken has been wholly satisfactory. For example, a direct projection of the image formed on the phosphor screen of a high intensity cathode ray tube provides an unsatisfactory display because the long persistence phosphors that are required for PPI presentations have an inherent low brightness characteristic. Long persistence phosphors are needed due to the very low frame sequencing frequencies, normally less than one cycle per second as determined by the antenna rotation period. Phosphors exhibiting a brightness that is sufficiently high for a direct screen projection have too short a persistence to be useful at the indicated low frame sequencing frequencies.

Various scan conversion techniques have been tried for the purpose of making the scan frequency of a PPI presentation compatible with the short persistence characteristics of high brightness phosphors. One method of scan conversion is to employ an image orthicon or vidicon to view the PPI phosphor screen, store the light information received and subsequently use it to drive a high intensity cathode ray tube of conventional parallel line scan. The low frame sequence frequency of the PPI tube is, in effect, converted into a high frame sequence frequency. The phosphor screen of the high intensity cathode ray tube can be readily projected. Another similar technique is to employ a double ended storage tube which provides essentially the same function as above described, but without the need for an optical coupling arrangement. Rather, a direct electronic connection is made within the tube.

The basic limitation existing in the above referenced approaches is that conventional TV cameras cannot accommodate the extreme range of signal brightness present between the initial flash of the phosphor and the persistent image existing some seconds afterwards. Further, the resolution of these equipments is relatively poor for most PPI display requirements. In addition, for a number of large area display requirements it is difficult to obtain phosphors of sufficient brightness, irrespective of persistence characteristics.

Another approach that has been considered is the use of photographic film wherein successive photographs of the PPI presentation are made and projected. This also has not proven to be satisfactory. Because a reusable photographic film is not yet available, it is necessary to consume large amounts of film in providing a continuous display. In addition, there is found to be a loss of orientation and integration by the viewer between successively projected frames. There is also a lack of target trails.

Thermoplastic recording has been adapted to PPI projection with some degree of success to provide a large area, bright display. In a thermoplastic recording process information is impressed by means of a radially scanned electron gun, as in conventional PPI cathode ray tubes. The information is written in a succession of frames on the thermoplastic film as it is transported from a feed reel to a take-up reel. The advantage provided by this system over those previously considered is that thermoplastic film can be used many times over. In addition there are no phosphor problems with respect to the projected information as in the aforementioned systems, and the projected image can be made quite intense. However, this system does hold some limitations. Since the spatial frequency of the radial scan lines at the center of the recording is extremely high, overlapping of the scan lines tend to occur in this area. Further, the radial line charges used in the recording are not compatible with efiicient Schlieren optics design. There is also difiiculty with respect to providing orientation and integration of the information between-successive frames, as there is in the photographic film embodiment previously discussed.

Accordingly, it is an object of the invention to provide a novel PPI projection system that makes possible a large area, high intensity display in a manner which overcomes many of the limitations existing in the prior art PPI projection systems.

It is a further object of the invention to provide a novel PPI projection system wherein target information and the like is impressed upon a light modulating medium employed to modulate projected light so as to provide a continuous large area, high intensity display of the impressed information.

It is a further object of the invention to provide a PPI projection system as above described which utilizes a deformable light modulating medium for phase modulating projected light.

It is still a further object of the invention to provide a PPI projection system employing a deformable light modulating medium, and including a novel projection optics which permits parallel scan lines rather than radial lines to be used for writing information on said medium.

It is yet another object of the invention to provide a PPI projection system utilizing a deformable light modulating medium wherein the object to be projected that is impressed upon said medium has a format that is compatible with the phase modulation projection optics employed.

It is another object of the invention to provide a novel projection system optics wherein information impressed on a cylindrical surface can be projected onto a plane surface with a corresponding circular configuration.

The various objects of the invention are accomplished in a novel projection system which basically includes a light modulating control medium arranged in a cylindrical configuration coaxial to the projection axis. The control medium has a base surface and an opposing first surface that provides a boundary between the control medium and a second medium having an index of refraction lower than that of said control medium. A light source transmits quasgcollimated light along the projection axis. Optical means are provided for directing the transmitted light uniformly through the cylindrical base surface of said control medium at an angle which provides a selective internal reflection of the light at said boundary as a function of information applied to said medium. Further optical means are provided for transmitting the selectively reflected light .in a direction approximately along the projection axis in a manner that forms a conical virtual image of the cylindrical object being projected. A telecentric lens means is employed to focus the reflected light as a real image of conical configuration at a distance from said virtual image. Further lens means transforms the focused conical image to a circular' planar image, which image is then projected to a large area display.

In one specific operable embodiment of the invention providing a PPI projection, the cylindrically shaped light modulating control medium is a deformable thermoplastic material deposited on a solid cylinder of transparent dielectric material having an index of refraction comparable to that of the thermoplastic. The thermoplastic medium has line charges written thereon by an electron gun. The line charges, which extend in the axial direction of the cylinder, present a differential charge pattern of the target information to be displayed and produce a corresponding deformation of the charge surface. The cylinder has a cutout portion in the shape of a pair of oppositely extending cones of common base coaxially arranged with respect to said cylinder. Light transmitted from the source enters the input base of the cylinder and becomes incident upon the input conical surface of the cutout portion which reflects the light so as to pass uniformly through the base surface of the thermoplastic film and be selectively internally reflected at the deformed surface in accordance with information impressed thereon upon said surface. The selectively internally reflected light is further reflected by the conical surface of the cutout portion so as to be transmitted through the base of the cylinder. A telecentric transfer lens means including a pair of lens elements and an intermediate spatial filter receives the light from the cylinder and focuses it onto a further conical surface. A fiber optics cone transforms the conical image into a circular planar image having radial lines which correspond to the axial lines of the cylindrical object, and a projection objective lens projects said circular planar image onto a display surface.

While the specification conludes with claims which set forth the invention with particularity, it is believed that the invention, both as to its organization and method of operation, will be better understood from the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is a schematic perspective view of the PPI projection system of the invention;

FIGURE 2 is an enlarged view of a portion of the deformable surface and graphically illustrating the light rays incident thereon, which view is employed in the description of the invention; and

FIGURE 3 is a schematic sectional view of the system of FIGURE 1.

With reference now to FIGURE 1, there is illustrated in schematic form a perspective view of a projection system 1 in accordance with the invention wherein a large area, high intensity display of PPI format is provided. Basically, the illustrated system projects an object of cylindrical configuration as a circular planar image, where parallel axial lines at the cylindrical surface are transformed into corresponding radial lines at the planar surface.

A light source 2 is provided which emits a quasi-collimated light of a desired intensity and collimation. A suitable high brightness source may include a standard high power xenon arc lamp, e.g., on the order of one to several thousand watts, in combination with conventional collimating lenses. Coaxially positioned on the projection axis along which light from source 2 is transmitted is a solid, transparent cylinder 3 having an input base surface 4 and an output base surface 5. Upon a central portion of the cylindrical surface of the cylinder 3 there is overlaid a light modulating control medium 6. In the specific operable example being considered the control medium 6 comprises a deformable thermoplastic material. However, other deformable light modulating control media, such as an oil film, may be employed, and control media of a density modulating type are also applicable to the system. The thermoplastic overlays a thin transparent conducting layer which is coated onto the cylinder surface. The cylinder 3 is made of a suitable vitreous or plastic ma- 4 terial having an index of refraction closely matched to that of the thermoplastic film. Since the thermoplastic is adhered closely to the external surface of the cylinder, there is provided essentially a continuous medium for light transmitted across the interface between the film and the cylinder.

In the embodiment being considered, information is impressed upon the exposed surface of the thermoplastic medium 6 as a series of line charges 7 by means of an electron gun structure 10. The differential charge pattern produced by the line charges form corresponding deformations upon the thermoplastic surface. The medium surrounding the thermoplastic film 6 has an index of refraction less than that of the film so that the deformed surface produces a selective internal reflection of the projected light incident at the surface from the underside, the internal reflections corresponding to the deformations of the thermoplastic surface. When employing an electron gun, the surrounding medium is normally a partial vacuum.

The electron gun structure 10 is of a conventional type and is schematically illustrated as including a cathode electrode 11, a control grid electrode 12, an accelerating anode electrode 13, a focusing electrode 14 and a scanning electrode 15. The electron beam 16 generated by the gun is modulated as a function of a given applied information and scans the cylindrical thermoplastic film in the axial direction of the cylinder. In the radar application under consideration, the distance along each scan line 7 represents target range information. A drive motor 17 is mechanically coupled to the cylinder 3 by a suitable linkage mechanism for slowly rotating the cylinder, the angular velocity of the cylinder corresponding to that of the antenna for supplying target azimuth information. In this manner, a conventional B-scan format is impressed upon the thermoplastic film, except that a cylindrical surface rather than a plane surface is employed.

A strip heater 18 is located in proximity with the thermoplastic film for softening the film so that the surface will respond to the line charges applied thereto. Other heating mechanisms may also be employed such as induction heaters and other types of radiant heaters.

The cylinder 3 has a concentric cutout portion 20 that is in the form of a pair of identically shaped cones having a common base and extending in opposite directions so that their apexes are in proximity with the input and output base surfaces, respectively, of the cylinder. The cutout portion 20 surrounds a medium having an index of refraction lower than that of the cylinder. The solid angle at the apexes of the double conical cutout portion is of a magnitude whereby light incident at the input conical surface 21 and the output conical surface 22 of the cutout portion is totally internally reflected thereby. Thus, the projected light incident at the conical input surface 21 is at an angle greater than critical and is totally internally reflected so as to be uniformly directed towards the thermoplastic film 6 and be incident at the undeformed surface of said film at the critical angle or slightly greater. Light selectively internally reflected at the surface of the thermoplastic film isincident at the output conical surface 22 at an angle greater than critical and is totally internally reflected so as to pass through the output surface 5 of the cylinder 3 approximately in the direction of the projection axis. Conical surfaces 21 and 22 are highly polished for providing an efiicient total internal reflection. They may, in the alternative, be coated with a reflective material so that an internal reflection at these surfaces is not necessary.

Light directed from the output surface 5 is intercepted by a telecentric transfer lens system 30 which includes a first transfer lens half 31, a spatial filtering mask 32 having a central aperture 33, and a second transfer lens half 34 identical to the lens 31. Although schematically illustrated as simple lens elements, in practice lens means and 31 are complex components. The telecentric lens system 30 is holosymmetric wherein the lenses 31 and 34 are of identical construction and are positioned at equal distances from the plane of the spatial filter 32. The lens system 30 forms of the cylindrical object impressed upon the thermoplastic surface a real conical image focused onto a conical surface 35.

The conical surface 35 forms the input surface of a fiber optics bundle 36 that is a cylinder having a cutout portion in the shape of a single coaxial cone having its apex extending to the output base 37 of the cylinder. The optical fibers of the bundle 36 which are tiny light conduits extending in the axial direction, transfer the conical image at the input surface 35 to the output surface 37 as a circular planar image, whereby the axial scan lines of the object appear as corresponding radial lines 41 in the circular planar image. A glass cone 42 having an index of refraction matched to that of the core elements of the fiber bundle 36 is bonded to the input surface 35. The glass member 42 is provided for substantially avoiding distortion producing reflective and diffractive effects upon light energy incident at the input surface 35. Thus, essentially a continuous light propagating medium is established between the solid glass body of the cone 42 and the fiber bundle 36. Further, the base surface 43 of the cone is normal to the projection axis so that light may cross this interface with little disturbance. Immersed fiber optics structures of this type are disclosed in greater detail in applicants copending application for US. Letters Patent, Ser. No. 561,863, filed June 30, 1966.

A drive motor 38, by means of a mechanical linkage, rotates the fiber optics bundle 36 so as to eliminate the structure of the fibers from the projected image. A projection objective lens 39, schematically illustrated, focuses the circular planar image upon a screen as a large area, high intensity PPI display. The projection lens 39 includes a counter-rotating prism (e.g., dove or pechan) to compensate for object rotation.

In the specific example being considered of a PPI projection, wherein a thermoplastic film is employed as the light modulating control medium, the writing process normally takes place in an evacuated chamber, not shown. The strip heater 18 is closely spaced from and surrounds the cylindrical thermoplastic film so as to heat the film to a softened condition in which it will respond to the deposited surface charge. The applied heat is adjusted to a level which permits the charge to gradually remove itself, by penetrating through the film surface, during the course of the cylinders rotation. In this manner as integration of the displayed information is provided between successive frames.

As an alternative technique, heat may be applied to only a limited portion of the thermoplastic surface by 'means of a narrow heating strip which is positioned adjacent to the writing station so as to heat the film immediately prior to writing. In this technique, previously applied charge is erased and new information can be applied and frozen into the thermoplastic surface after that portion of the film passes the writing station and cools. It should be noted that the precise manner in which information is written is not critical since the invention is concerned primarily with the optics of projecting information contained by the cylindrical surface.

In the projection process, light transmitted through the base surface of the thermoplastic film 6 is incident at.

' illustrated, in a greatly enlarged view, a portion of the deformable surface including an undeformed segment a, an intermediately deformed segment b and a maximumly deformed segment 0. The undeformed segment a corresponds to a bright element of the display, the intermediately deformed segment b to a gray element and the maximumly deformed segment c to a dark element. Light rays striking the undeformed segment, represented by ray X, are incident at the surface at the critical angle or slightly greater and are totally internally reflected in a given direction. Light rays striking the surface of the intermediately deformed segment, shown by ray Y, are incident at the surface at an angle somewhat less than critical. Some of the energy is transmitted through the surface and the remaining energy is reflected in a second direction slightly offset from said given direction. Light rays striking the maximumly deformed segment, shown by ray Z, are incident at the surface at a still smaller angle than with respect to incident ray Y, appreciably less than critical. A smaller percentage of the light is reflected than as in the previous case, which light is in a third direction somewhat further offset from said given direction.

Thus the reflected energy has both a varying intensity and a varying direction which are a function of the magnitude of the deformations. Upon being transmited through the telecentric lens system 30, the spatial filtering mask 32 acts to demodulate the phase information by partially blocking the transmitted light as a function of its direction. The light my X reflected from the undeformed surface is internally reflected by the output conical surface 22 in a direction along the projection axis and will pass through the center of the aperture 33 of mask 32. The light rays Y and Z reflected from the deformed surfaces are reflected by output conical surface 22 so as to be off the projection axis and thereby partially or completely blocked by the mask as a function of the deformations. A more detailed description of selective internal reflection projection from a deformable surface is presented in a copending application entitled Total Internal Reflection Projection System, Ser. No. 222,844, filed Sept. 22, 1962, by M. L. Noble and assigned to the assignee of the present invention.

Referring now more particularly to the projection optics of the present system, in FIGURE 3 there is..illustrated a schematic diagram of the systems optical components taken in a cross-sectional view. Two pair of light rays A, B and C, D existing in a single plane are shown. It may be appreciated that similar rays exist in every other plane that can be drawn through the axis of the system. Rays A, B are incident on a line on the upper half of the conical input surface 21, and rays C, D a e incident on a line on the lower half of said conical surface. Thus, rays A, B are totally reflected upward so as to be incident at the deformable surface on a first axial line and rays C, D are reflected downward so as to be incident at the deformable surface on a second axial line at the opposite extremity of the cylindrical surface. In a similar manner, the entire bundle of projected light rays incident at the input conical surface 21 is reflected through 360 so as to uniformly illuminate the entire cylindrical deformable surface.

Light rays A, B are reflected by the thermoplastic surface so as to be incident on a line on the upper half of the conical output surface 22 and rays C, D are reflected so as to be incident on a line on the lower half of said conical surface. The above statement presumes the absence of a lateral scattering of the light rays by the deformable surface outside of the plane under consideration. In fact there will be lateral scattering but such does not effect any significantly different operation of the system from the in-plane light rays and for purposes of simplifying the explanation will not be further considered.

Light ray A is seen to illuminate and be reflected at the film 6 from the end of said first axial line upon which so as to be transmitted through the central portion of the telecentric lens elements 31 and 34 and through aperture 33, focused at the region of the apex of the conical surface 35 and projected by lens 39 to the central region of the image formed on the screen 40. Light ray B illuminates and is reflected from the end of said first axial line that is further from the projection screen. Light ray B is reflected by the output conical surface 22 so as to be transmitted through the upper peripheral portion of the first telecentric lens 31, through the aperture 33, through the lower peripheral portion of the lens 34 and focused on the lower peripheral portion of the conical surface 35. The focused light is conducted through the fiber optics cone to the output base 37 and from there projected to the upper peripheral region of the image on the screen 40. If the surface in the region of the first axial line is deformed, light rays A and B will be reflected therefrom at a phase and amplitude modulation so as to be projected upon the screen with a diminished intensity that is a function of the deformations, as has been described. In corresponding manner to the projection of light rays A, B rays C, D are selectively reflected at points on said second axial line of the deformable surface, transmitted through the telecentric lens system 30, focused onto the upper half of the fiber optics conical surface 35 and projected to the lower half of the image on the screen 40. Accordingly, it may be seen that the cylindrical object formed on the deformable surface has its configuration changed by the projection system so that the linear edge of the object closest to the screen is projected to a much constricted central region of the projected image and the opposing linear edge of the object is expanded and projected as the peripheral edge of the projected image.

In the projection .process, within the cylinder 3 there is formed a virtual conical image of the object, which is represented in FIGURE 3 by the broken lines A'B and C'-D'. The telecentric lens system 30 acts to transfer this image outside of the cylinder as a real image so that it can modifications and alterations may be made which do not exceed the basic teaching set forth herein. As stated previously, other forms of light modulating control media can be employed, for example, density modulating media such as photographic film, and other kinds of phase modulating media including those operating on light scattering principles. When employing a density modulating medium, it is not necessary to employ a spatial filtering mask since there is no phase modulation of the reflected light but purely amplitude modification. In addition, there are other means known to the art for transferring an image from .a conical surface to a corresponding planar surface other than the disclosed fiber optics bundle. A series of elemental lens components may be employed for this purose.

p Although the invention is primarily concerned with the projection of a PPI format, it very basically teaches a projection system for projecting a cylindrical object as a circular planar image and may be useful for mapping functions and other functions that require such projection transformation.

Further, it is noted that an internal reflection projection system is specifically disclosed, which system has' a number of advantages not the least of which is the ability to write and project from the opposite sides of the modulating medium, thereby avoiding interference between the two apparatus. However, the invention would also have application to a transmissive system wherein the pro ection optics on the input side of the modulating medium is arranged to transmit light uniformly through the modulating medium, entering at its external surface and exiting from the opposite surface. For this operation the input conical surface 21 as such would not be required. In lieu there might be employed a conical surface, having a slope of the same polarity as the output conical surface 22, arranged externally of the cylindrical object, for reflecting projected light toward the medium.

The appended claims are intended to include within their meaning all form of modification and variation that reasonably fall within the true scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A projection system for projecting a cylindrical object to a planar surface as a corresponding circular image, comprising:

(a) a light modulating control medium arranged in a cylindrical configuration to which information is applied so as to form said object,

(b) first optical means for directing projected light through said control medium so as to be selectively modulated in accordance with said information,

(c) second optical means responsive to the selectively modulated light for focusing said object as a corresponding conical image, and

(d) further optical means for transforming said conical image into a circular planar image.

2. A projection system as in claim 1 wherein said second optical means includes a conical surface disposed inward of said control medium.

3. A projection system as in claim 2 wherein said second optical means further includes a telecentric transfer lens means.

4. A projection system for projecting a cylindrical object to a planar surface as a corresponding circular image, comprising:

(a) a light modulating control medium arranged in a cylindrical configuration to which information is applied so as to form said object, said control medium having a base surface and an opposing surface that provides a boundary between said control medium and a second medium having an index of refraction lower than the index of refraction of said control medium,

(b) first optical means for directing projected light through the base surface of said control medium at an angle that provides selective internal reflection of said light at said boundary in accordance with the applied information,

(c) second optical means responsive to the light selectively internally reflected at said boundary for focusing the object as a corresponding conical image, and

(d) further optical means for transforming said conical image into a circular planar image. I

5. A projection system as in claim 4 wherein said control medium is coaxially arranged with respect to the projection axis of the system and including means for transmitting said projected light with quasi-collimation properties along said projection axis towards said first optical means.

6. A projection system as in claim 5 wherein said first optical means includes an input conical surface coaxially arranged with respect to said projection axis and inward of said control medium, said conical surface reflecting the incident projected light away from the projection axis towards said control medium. l

7. A projection system as in claim 6 wherein said second optical means includes a coaxial output conical surface of inverse slope with respect to that of said input conical surface for directing selectively internally reflected light from said boundary substantially along said projection axis toward further optical means.

8. A projection system as in claim 7 wherein said control medium overlays the cylindrical surface of a solid transparent cylinder having a central cutout portion in the shape of oppositely extending cones of common base, which cones form said input and output conical surfaces.

9. A projection system as in claim 8 wherein said solid transparent cylinder has an index of refraction approximately equal to that of the overlaid control medium.

10. A projection system as in claim 9 wherein said second optical means further includes a telecentric transfer lens means for focusing the light reflected from said output conical surface onto a further conical surface.

11. A projection system as in claim 10 wherein said further optical means includes a fiber optics bundle of cylindrical configuration having said further conical surface as its input surface and a planar output surface, said fiber optics bundle conducting the light incident at its input conical surface to its planar output surface so as to transform the conical image at the input surface to a circular planar image at the output surface without appreciably distorting the focused image.

12. A projection system as in claim 11 wherein said further optical means includes an objective lens for focusing said circular planar image onto a large display area.

13. A projection system as in claim 12 wherein said control medium includes a deformable thermoplastic material, said input information being applied in the form of deformations impressed upon said opposing surface.

14. An optical component for providing transformation of a cylindrical object to a corresponding conical image, comprising:

(a) a solid transparent cylinder upon the cylindrical surface of which is intended to be formed said object, said cylinder having an index of refraction greater than the surrounding medium, and

(b) said cylinder having a central cutout portion in the shape of a pair of oppositely extending cones of common base disposed along the axis of said cylinder, the conical surfaces of said cones forming an angle with said axis which provides reflection of axially directed light toward said cylindricalsurface at an angle that exceeds the critical angle.

15. An optical component as in claim 14 wherein said cutout portion contains a medium having an index of refraction lower than that of said cylinder so as to provide an internal reflection of said light at said conical surfaces.

References Cited UNITED STATES PATENTS 2,430,616 11/1947 Pearson 2401 2,781,706 2/1957 Higonnet et al 4.5 2,928,952 3/ 1960 Bednarz 8824 FOREIGN PATENTS 676,025 12/1963 Canada.

NORTON ANSHER, Primary Examiner.

WYNDHAM M. FRYE, Assistant Examiner. 

1. A PROJECTION SYSTEM FOR PROJECTING A CYLINDRICAL OBJECT TO A PLANAR SURFACE AS A CORRESPONDING CIRCULAR IMAGE, COMPRISING: (A) A LIGHT MODULATING CONTROL MEDIUM ARRANGED IN A CYLINDRICAL CONFIGURATION TO WHICH INFORMATION IS APPLIED SO AS TO FORM SAID OBJECT, (B) FIRST OPTICAL MEANS FOR DIRECTING PROJECTED LIGHT THROUGH SAID CONTROL MEDIUM SO AS TO BE SELECTIVELY MODULATED IN ACCORDANCE WITH SAID INFORMATION, (C) SECOND OPTICAL MEANS RESPONSIVE TO THE SELECTIVELY MODULATED LIGHT FOCUSING SAID OBJECT AS A CORRESPONDING CONICAL IMAGE, AND (D) FURTHER OPTICAL MEANS FOR TRANSFORMING SAID CONICAL IMAGE INTO A CIRCULAR PLANAR IMAGE. 